Natural populations of the yellow fever mosquito, Aedes aegypti will be analyzed to determine nucleotide sequence heterogeneity in mitochondrial DNA. Sequence divergence among individal isofemale lines from field collected populations will be detected by comparing the DNA digestion patterns obtained using a minimum of 6 different DNA restriction endonucleases. Populations analyzed will be from throuhout the broad geographical distribution of the species. The analysis will permit the ascertainment of genetic relatedness of conspecific populations which will be used to describe the evolution of this species. Probable origins of newly introduced populations of A. aegypti in different areas of the world will be deduced from estimates of genetic relatedness based on nucletide sequence divergence. Methods and techniques developed for the assay of nucleotide sequence divergence will be used in collaborative studies concerning the genetic basis of vector competence for arboviruses. Strains of A. aegypti, tested for efficiency as competent vectors of yellow fever, will be analyzed to determine sequence divergence for mitochondral DNA. Estimates of genetic relatedness will be determined between strains and individuals differing in vector competency.